DanWho

I am reading all sorts of different things about us bigger clydes riding on smaller tires and at the same time I am also reading some riding on the skinny tires at high pressures with out problems.

For instance I read one place that with 28mm tires at 125psi they could handle a rider of about 280#, but then I will read somewhere someone is running 25s or 23s at the same weight and roughly the same pressures. Is there a definitive size and weight table around or is it just try it and see?

prathmann

There are some tables around that claim to be pretty definitive, but it will also depend very strongly on the condition of your roads and your particular riding style. Someone who chooses (and has available) nice smooth roads and rides carefully to avoid any potholes or bumps and lifts his weight off the saddle for the ones that can't be avoided can get away with much skinnier tires at lower pressure than the person who rides on rough roads and barrels right through the potholes while keeping their weight on the saddle.

But here's one of the calculators:
Bicycle tire pressure calculator

[I feel this method underestimates the front tire pressure needed since it ignores the weight shift to the front that occurs when you hit the brakes - as you might do when you see a big bump ahead. And, as stated, there's the dependence on riding style and road condition.]

GravelMN

There is very little, if any, advantage for a Clyde to choose 25mm tires over 28s as long as the frame has adequate clearance. In the chart below, with a rider and bike combined weight of 260#, assuming that the rear wheel takes about 55% of the load (143#), the recommended pressure would be about 110 psi for the 28mm and nearly 130 psi for the 25mm.

https://www.bikequarterly.com/images/TireDrop.pdf

The higher pressure in the 25mm tire is going to make for a harsher ride and possibly even more rolling resistance than the same model of tire a size bigger at the lower pressure. The very slight weight and aerodynamic advantages of the narrower tire would be more than offset by the disadvantages.

mkadam68

Charts? Calculators? Garbage. The calculator above said I needed to run my 23c rear wheel at 194 pounds! Ha! (The first said over 300 pounds!) The chart had me exceeding 154 pounds and it wasn't even finished. I've only ever ridden tires higher than 120-pounds once. I had some Vreddestein's, rated to 140 pounds. I tried 140 once. Terrible. Rear wheel jumped all around whenever I got out of the saddle. I had very little traction.

There's two numbers you need to be concerned about:

• the maximum the tire can be inflated to and
• the maximum the rim can handle.

Pump up to the lesser of those two numbers one day, ride it, decide if you like it or not. Was it too hard? Was the rear wheel jumping around, clattering over rough spots? Did it beat you up while riding it? If so, lower it 10-pounds, try it again. Repeat. If you liked it, you've found what you were looking for.

dr_lha

Just try and see.

chaadster

Yeah, I'd have to agree given that most don't comport with reality.

I don't know anyone riding the kinds of PSI recommended by the above calculators, but know plenty of clydes on 23s, myself included, who ride about 120psi on Michigan's famously poor roads, well-and-far below the claptrap recommendation (north of 150psi, but off the chart, literally) in the BQ pdf.

One set of 23c tires I run at 90F/105R, but it's a tubeless setup with a 19.4mm inner width, so the 23s plump out to easily meet 25c proportions. So, it's not only about tire width, but rim inner width.

I've tried 25c on standard width (19.4mm brake track, 14.9 internal) and hated the feel, especially on the front, for performance riding. I could feel the slip between the road surface and rim edge when the tire was cranked over in a turn or when I was honking on the bars as during a sprint. This was Michelin Pro Optimum 25c on Mavic Open Pro; I had to run the tire pressure higher to avoid the sloppiness, which ruined the feel.

Anyway, it's probably true that for general riding and most riders, there's nothing against 28c tires for clydes, and I do run 85psi 28c on my commuter, but stretched out across 28mm outer/23mm inner Velocity Blunt rims, so they handle crisply.

EDIT: I had to chuckle when I saw my 28c psi is even under, by more than 15lbs, the BQ chart. C'mon, guys, seriously, what's up?!

Wanderer

You don't say how much weight you will be hauling, nor the type of roads, nor the tire size you will have.

Bill Kapaun

You have to pick the combination that works best for your weight and road conditions.
I love skinny tires on my hybrid.
I tried a 23mm on the front and I just got too much "road buzz" from rough textured pavement.
Not so with my 25mm's at my 250 lbs.

You MUST run high enough pressure so that you have enough "squish factor" to not damage a rim/get pinch flats if you do hit a pot hole, no matter what size tire you use.

sstorkel

Good advice. The various tire pressure calculators, charts, and formulas are all designed as guidelines for people of average weight. If you're significantly lighter or heavier than average, the guidelines won't necessarily work for you. Those heavier than average will likely be limited by the maximum pressure their tire and rim can handle. If the ride is too harsh, you can consider lowering the pressure but if you lower it too much you may be subject to pinch flats.

GravelMN

I agree that charts and calculators are just references and not stone tablets brought down from the mountain, but I ran all three calculators on that page and they aren't horribly off for me. I weight 230# and my bike is about 25#. The results for the rear wheel (only one specified front/rear) came to 114, 127, and 116 psi for a 25mm tire. The 127 was for the back tire from the one calculator that gave both front and back. The front tire pressure was calculated at 102 psi or an average between f/b of 114 psi. So if I calculated 45% front and 55% rear based on each of the results they all came in at about 102-105 front and 125-127 rear. Not far off for a 255# combined bike and rider weight. I have run Specialized Armadillo Elites, Bontrager AW3 Hardcase Lite, and Continental Ultra Sport II in 25mm on my steel road bike and after some experimentation, I run about 110-115 psi in the front tire and 120-125 psi in the rear. My Bontrager tires have a max pressure of 125 psi listed on the sidewall, so everything is in sync.

When using the calculators, did you enter the weight per wheel on the first one and not the overall bike and rider weight?

DanWho

I call myself 6' 1 1/2" tall due to the fact that when ever I am measured I am either 6' 1" or 6' 2". I am just under 300 down from 352 last year. I just got a bike, quintana roo kilo, the person I got it from was using 20mm tires on it. (I hate him LOL). It has 650c rims. I just put on some 28mm tires which the sidewall says max at 125. All the different calculators say something different. One says that at 125 psi I can weigh a max of 280, another says that IF I air them up to 175 rear and 160 front I could ride them at 295, another said right at 200 psi for 300.

This bike looks tiny enough as it is, the last thing I don't want to happen is for me to jump on it and have both tires blow out. That would be very BAD for my fragile ego.

mikiek

Rim width pays a big role in what tire pressures you can use. Normally the wider the rim the lower the pressure you can get away with on the same tire. So 28mm tires at 125psi doesn't tell you the whole story.

Keep in mind that the psi ranges you see on tires are usually calculated for the common 19.x mm width rim. I actually contacted Continental and asked their recommendation for a 25mm width rim and the numbers they gave were a little lower that what the tire says.

DanWho

In all my searching I only found one place that had specially made 28mm tires and from what I understand, I don't think there is anyone that does anything other than the 19mm rims for 650c. They are still something of an odd duck still mostly on tri bikes. I had found one offroad tire but it was way too big to fit inside this bike. Even with the 28s I could only install them deflated, if the rims start to go out of true I will know right away. I don't think that a 32mm tire will fit within the confines of the bike.

Willbird

Just thinking out loud, can you build a wheel using a 26" rim ?? According to Sheldon that is an ISO 559, the 650c is ISO 571(12mm bigger dia ...6mm on the radius).

Harris Cyclery has a variety of tires.

https://sheldonbrown.com/harris/tires/559.htmlC

could be way over my depth here :-)

Kinlin MTB Rims

BHS appears to have some rims.

Bill Kapaun

Seems like a pretty expensive GAMBLE!
Brakes would have to have enough adjustment.
OP doesn't think 32MM tires would fit.
So, WHAT rim & tire would you use?
Even if the brakes still worked, the OP would still be painted in the same corner.

It's simply a matter of "this bike is not appropriate" for the weight of the OP.

Willbird

Well I look at "thinking" as an exercise, stretching the grey matter :-).

Putting one type of 26.5 (the 650B) onto 700c bikes was something Sheldon spoke of, and in that article he did say that using a smaller dia rim allowed some room for a wider tire.

Wheels are often the weakest part of any bicycle system, and being stuck with just a few 23mm wide tires would totally suck :-).

But an idea is never a bad thing, and anybody with any sense would do a search and see if maybe 8 other people already put 26" wheels and tires into 650c frames to be able to use wider tires than 23mm :-). So :-P :-).

Bill

Bill Kapaun

You have to pay a little bit of attention to the bike brand & model that the OP has!

Willbird

Do I ??

Not as I see it, yes there could be other issues than just using a smaller rim....but still mental exercise is a good things.

28's OUGHT to work though as far as that goes, I agree that THAT bike is not suited to running say 35's ;-).

Bill

DanWho

I got the bike because it was a great price and as an incentive to continue loosing weight. I'm already trying a little harder to get down faster so that I can play with it.

I thought about the same things with using 26 inch tires, doing that I just might be able to stuff a 32 in there if the wheels are perfectly true. The thing is I would have to look for longer reach brakes or do some creative engineering. The pads will only go down another 2mm or so.

Right now it is in the stand yelling at me do you really need the sweet in your sweet tea?

Willbird

Are you pinch flatting tubes now ?

DanWho

After putting the 28mm tires on and airing them up, I have left it hanging on the repair stand until either I loose another 20-30 lbs or have to fix something on the other bikes. This is my big incentive to loose more weight faster so I can ride it. For right now I plan to let it hang there and taunt me.

Jarrett2

275 lbs
700x25mm @ 120 psi, no probs
700x28mm @ 100 psi, also no probs, just a little slower and more sluggish than the 25's. Although slightly more comfortable.
Gatorskins, GatorHardshells or Specialized Armadillo Elites.

DanWho

I could only find one place that sells 28mm Serfas Urbana 650cx28 and it is specially made for one bike shop. R + E cycles out of I think it was portland. There were several 25mm and a slew of 23mm and the bike came with 20mm so I know that someone makes them, didn't pay attention who. If I left the 20mm on I probably blow them out by putting my arm on the seat.

chaadster

Forget the 28c tires. It's *extremely* unlikely they will fit. I'd bet 25c don't fit either.

Either air up a pair of 23c to 125-130psi and ride it, or sell it and get something better suited to your needs. Or keep it and get something else better suited to your needs.

DanWho

I got the 28mm to fit, just couldn't air them up until they were mounted. There is probably 2-3mm of space left over. I had some fun truing the wheels to keep a good even space all around. I will definitely if the wheels start to loose true. I am thinking this weekend I may get brave and at least give it a test spin. I aired the tires to the 125psi sidewall max and will go from there. I just hope that I don't jump on and immediately blow out the tires, I would feel really bad and I'm sure the GF and daughter would say " see it is too pretty and tiny for you, give it to me."